1. Technical Field
The present invention relates generally to vehicle adaptive cruise control systems, and more particularly to a method and apparatus for adjusting vehicle speed and inhibiting vehicle resume speed when a ramp is detected.
2. Background of the Invention
Adaptive Cruise Control (ACC) has reached a level of technical and business readiness that it is beginning to appear in the consumer market as a comfort and convenience system. Consumer technical enthusiasm for ACC has increased because of their interest in intelligent vehicles and systems such as collision warning. ACC performs as an enhancement to traditional cruise control by automatically adjusting the set speed to allow a vehicle to adapt to moving traffic.
Under normal driving conditions the ACC system is engaged with a set speed equal to a maximum autonomous speed which is desired by the operator, referred to as a set speed, and the ACC system operates in a conventional cruise control mode. The ACC system continuously adjusts the speed of the vehicle to maintain the set speed. The ACC system uses radar to detect target vehicles in a future path of the vehicle. When the vehicle approaches traffic, thereby becoming a follow vehicle, the ACC system automatically adjusts the set speed to follow the traffic at a desired headway distance. The desired headway distance is a predetermined distance that the follow vehicle remains behind a detected target vehicle. When the traffic clears or the follow vehicle changes lanes the ACC system slowly resumes the speed of the vehicle back to the set speed. When the follow vehicle approaches slow traffic the ACC system is automatically disengaged and the operator manually follows slower vehicles in the slow traffic. When the slow traffic is no longer in front of the vehicle the operator pushes the resume button and the ACC system accelerates the vehicle back to the set speed.
Current ACC systems are unable to detect the difference between a road and an exit ramp. Therefore, the follow vehicle may accelerate to the set speed when entering an exit ramp and no longer detecting a target vehicle.
It would therefore be desirable to develop an ACC system that adjusts the vehicle resume behavior in response to the presence of a ramp.